Yellow-eyed penguin

Yellow-eyed penguin / hoiho

Megadyptes antipodes

Thomas Mattern & Kerry-Jayne Wilson Document date: 12 April 2019; DOI: 10.36617/SoP.hoiho.2019-04


The yellow-eyed penguin / hoiho (Megadyptes antipodes) is endemic to New Zealand. It occurs along the south-eastern coastline of the South Island, on Stewart Island and its outliers, as well as the sub-Antarctic Auckland and Campbell Islands. The species is now the world’s second-rarest penguin species with an estimated 1,700 breeding pairs across its entire distributional range. The species is listed as ‘endangered’ by the IUCN red list and is considered ‘nationally endangered’ by the New Zealand Department of Conservation’s threat ranking system.

The yellow-eyed penguin is one of the best-studied species in New Zealand with the first comprehensive population study conducted as early as the 1930s and a string of research projects that investigated various aspects of the species biology since the 1980s. Most of this research occurred on the New Zealand mainland, with very little information from the sub-Antarctic populations. A phylogenetic study found that there is very little gene flow between the mainland and sub-Antarctic populations, or between the two sub-Antarctic islands, so that the three subpopulations must be considered separate management units.

The species’ mainland population has been undergoing a steady and significant decline since the mid-1990s, a trend that appears to continue; population projections predict local extinction on the mainland by 2060. While the sub-Antarctic islands are often considered to be the species’ stronghold, because they were home to a large proportion of the population in the late 1980s and early 1990s, there is no recent data to show if this is still true. Climate change has been identified to be an important factor contributing to the yellow-eyed penguin decline on the mainland, and might have caused a shift in the penguins’ prey from smaller fish (e.g. larval red cod, Pseudophycis bachus) consumed in the 1980s to large prey items (mainly juvenile and adult blue cod, Parapercis colias) since the 1990s. This may have consequences for reproductive success, with larger prey items unsuitable food for chicks, leading to starvation and facilitating disease outbreaks. However, climate change alone does not explain the population decline and it is suspected that fisheries interactions, pollution and human disturbance have all contributed to the species’ dire status.

On the mainland, yellow-eyed penguins are predominantly benthic foragers that principally pursue demersal fish species. This makes them vulnerable to accidental bycatch in set nets with poor foraging on seafloor habitats degraded by bottom fishing activities such as dredging and bottom trawls. Adult survival appears to be too low to sustain the population and may have led to an imbalance between the sexes with male penguins now outnumbering females. In recent decades, disease outbreaks have affected reproductive success, and several die-off events have reduced the breeding population further.

Previous reviews of biology and priority lists

The first major review of the yellow-eyed penguins’ breeding biology was compiled by Lance Richdale who studied the species between 1936 and 19541–3. A comprehensive review was later compiled by John Darby4.

Research and conservation priorities were listed by Taylor5. He proposed that habitat protection and restoration, and introduced predator control should be of highest priority, followed by advocacy to mitigate fisheries impacts, better control of dogs, and establishment of guidelines to manage visitor access to mainland colonies. These recommendations were developed further in the yellow-eyed penguin recovery plan6. While habitat protection, restoration, and pest control efforts have improved since then7, fisheries impacts have not been adequately addressed8,9. Likewise, predation by uncontrolled dogs (Melanie Young, pers. comm.), and unregulated visitor access at some mainland sites remain issues.

Taylor5 also recommended surveys be undertaken, with continued annual monitoring on the Otago Peninsula being a high priority as well as population counts on Stewart Island and the sub-Antarctic islands. While monitoring on the Otago Peninsula has continued10 and a survey of Stewart Island was conducted in 1999/200011, there is no reliable recent information on population size for either of the sub-Antarctic populations12. Some of the research priorities listed by Taylor5 have been addressed in the last two decades. These include phylogenetic studies across the species’ distribution13–16, analysis of long-term survey data to estimate population sizes and trends10,17,18, and tourism impacts19–22. Some other recommendations currently being addressed, are factors affecting recruitment rates (Melanie Young, University of Otago) and some aspects of the species’ biology on the Auckland Islands (Chris Muller, Massey University). Overall, priorities need to be revised in the light of the species’ continued decline on the New Zealand mainland.

In 2012, a comprehensive review of yellow-eyed penguin biology and population trends on the mainland emphasised the importance of fisheries’ impacts8. This was followed up by a species review by Seddon, Ellenberg & van Heezik12. Most recently, a substantial literature review was published by the Yellow-eyed Penguin Trust which took a more system approach to management suggesting the management of factors extrinsic to the species7. All of the reviews include priority lists for research and conservation actions that reflect or expand on Taylor5.

Conservation status

The Department of Conservation lists the Yellow-eyed penguin as ‘nationally endangered’ criteria C(1/1) (1000-5000 mature individuals, predicted decline 50-70%), qualifier EF (Extreme Fluctuations)23. The IUCN red list classifies the species as ‘endangered’ with selection criteria B2ab(ii,v)c(iv) (area of occupancy <5000 km², fragmented distribution, ongoing population decline and extreme fluctuations in the number of mature individuals24.

The Yellow-eyed penguin is the only penguin species in New Zealand with a dedicated recovery plan6. A severe die-off in 1989 triggered years of intensive monitoring and research to understand that mechanisms that are contributing to the species’ apparent population decline25–29. The recovery plan aimed to “manage the hoiho population by providing a framework for community and DOC initiatives to actively enhance hoiho numbers”. Nine objectives for the recovery of the species were outlined, seven of which focussed on terrestrial aspects of the species management, i.e. monitoring, protection and improvement of breeding habitat, predator control, management of tourism activities, and advocacy. The two other objectives were concerned with identifying the impact fisheries had on survival rates, and research that would assist the other objectives6.

New research into the marine ecology of the species in the 2000s suggested that the species was facing serious threats at sea30–33. Examination of genetic diversity highlighted the need to consider the mainland and the sub-Antarctic populations as three separate management units14.

To re-assess the objectives outlined in the recovery plan, a comprehensive stock take was conducted in 201534. This found that the “current [recovery] plan is no longer fit-for-purpose for the future, although many of the objectives and actions are still relevant”. That report lists a number of recommendations suggesting which directions a revised recovery plan should take but does not provide clear objectives. Therefore, for the time being, the original recovery plan remains the primary guideline for the recovery of the species. The recent review of the species’ management by Webster7 should provide additional guidance.


The yellow-eyed penguin is the single remaining representative of the genus Megadyptes. Genetic analysis using ancient DNA revealed that the New Zealand mainland was originally inhabited by a sister-taxon, the Waitaha penguin; Megadyptes waitaha13, which is believed to have been hunted to extinction within a few hundred years of Maori settlement in New Zealand13. The loss of M. waitaha allowed the yellow-eyed penguin to expand its range from the sub-Antarctic Islands from the 15th century onwards15.

Despite this historic colonization of yellow-eyed penguins from the sub-Antarctic, there is apparently very little contemporary gene flow between the three main breeding locations of the species; the mainland, Auckland Islands and Campbell Island14,16. Both Triggs & Darby16 and Boessenkool et al.13 recommended each of the three subpopulations be considered separate management units for conservation.


Yellow-eyed penguins have probably only bred on the South Island for the last several hundred years. Ancient DNA analysis and radiocarbon dating show they expanded their range from sub-Antarctic New Zealand following extirpation of its sister taxa, Megadyptes waitaha. Bones of M. waitaha are relatively common in coastal dune deposits and archaeological midden sites13,35–39. The rapid extinction of M. waitaha15 is indicative of the vulnerability of these penguins; a salutary lesson for today’s penguin conservation workers.

Yellow-eyed penguin nest on Stewart Island.

Figure 1. Typical Yellow-eyed penguin habitat on Stewart Island, Rollers Beach. (Photo: Thomas Mattern)

On the New Zealand mainland, the core breeding range of Yellow-eyed penguins is the Otago and Southland coastlines from Bushy Beach, Oamaru (-45.118°, 170.972°) south to Slope Point, Catlins (-46.670°,169.003°). There are a few breeding pairs on Banks Peninsula, but they exhibit poor breeding success and recruitment into the Banks Peninsula population comes from further south12. Yellow-eyed penguins also breed on Stewart Island / Rakiura (-46.856°, 167.913°) and some of its satellite islands including Codfish Island / Whenua Hou (-46.772°, 167.624°)11,17.

One of the sub-Antarctic yellow-eyed penguin populations is on the Auckland Islands (-50.745°, 166.054°), some 500 km south of the New Zealand mainland. The majority of penguins apparently breed on Enderby Island at the northern end of the archipelago (-50.497°, 166.302°)40. Whether the species breeds at other places around the archipelago in significant numbers is unclear; a survey of the eastern coastline of the main island, as well as Carnley Harbour and Adams Island identified 306 potential Yellow-eyed penguin landing sites but could not assess penguin numbers41. Based on the survey it appears as if Yellow-eyed penguins are clustered in the north (Enderby, Ewing and Frenchs Islands) and south (north-coast of Adams Island) of the Auckland archipelago.

The second sub-Antarctic population of yellow-eyed penguins is on Campbell Island (-52.539°, 169.148°)40,42. The penguins predominately inhabit inlets and sheltered bays, including Northeast and Perseverance Harbours to the east and Southeast and Monument Harbours in the south. The largest concentration of birds occur in Northwest Bay on the western promontory of Campbell Island40,43.

Juvenile and non-breeding adults may range far beyond the breeding distribution. Fledglings satellite tracked in 2017 and 2018 ranged as far north as Kaikoura with one bird even making landfall in Clifford Bay at the northern tip of the South Island. Juvenile and non-breeding or moulting adult penguins have been seen as far north as Taranaki and Hawke’s Bay44.

Numbers and population trends

The current red list estimate of the yellow-eyed penguins’ total population size of 1,700 breeding pairs24 is effectively pure speculation. The majority of these are believed to live on the two sub-Antarctic islands, with an estimated maximum of 600 pairs on Campbell Island and 570 pairs on the Auckland Islands40. However, population estimates for both islands date back to the late 1980s and early 1990s, a time when numbers of Yellow-eyed penguins on the mainland were considerably higher than now (Table 1). In 1996, a total of 635 nests were counted on the New Zealand mainland (excluding Stewart Island and its outliers); just 252 nests were found in 2017 (Department of Conservation, unpublished data). On the Otago Peninsula, the yellow-eyed penguin population has declined by as much as 75% in the past two decades10.

Table 1. Population estimates of yellow-eyed penguins in New Zealand.
Year of count Location Number of breeding pairs Reference
1988-1989 South Island 300-320 Peter Moore40
1996 South Island 635 DOC, unpublished data*
2011-2012 South Island 454 Seddon, Ellenberg & van Heezik12
2017 South Island 252 DOC, unpublished data**
1988-1989 Stewart Island 470-600 Peter Moore40
1989-1990 Stewart Island 300-400 Marchant & Higgins45
1934-1994 Stewart & Codfish Island 220-392 John Darby17
1999-2001 Stewart & Codfish Island 178 Massaro & Blair11
2008-2009 Stewart & Codfish Island 153 Seddon, Ellenberg & van Heezik12
1988-1989 Auckland Island 520-570 Peter Moore40
1988-1989 Campbell Island 490-600 Peter Moore40

Current population trajectories on the New Zealand mainland point towards local extinction in the next two to four decades10. While these predictions are based on monitoring data collected at Boulder Beach on the Otago Peninsula, subsequent data analysis found these trends to be hold across the mainland except for two intensively managed penguin populations, Katiki Point (-45.395°, 170.868°) and Barracouta Bay (-45.392°, 170.858°)46. Penguin numbers have declined on Stewart Island47 and Codfish Island (Yellow-eyed penguin Trust, unpublished data).

There is evidence for population variation in the sub-Antarctic - at Campbell Island the population decreased by 41% between 1988 and 1992, with at least a partial recovery over the next six years48. These data were based on whole island beach counts and mark-recapture analysis at study sites. Due to the lack of robust survey data since then, it is not possible to make any definitive inferences about population trends in the past 20 years. Beach counts conducted between 2001 and 2012 on Enderby Island, Auckland Islands, have suggested an increase in penguin numbers49. However, the counts were conducted on a single day each year and then towards the end of the breeding season (i.e. February) when the nest attendance patterns and hence penguin movements are highly variable50. As a result, the beach count methodology employed does not provide a robust population trend assessment, particularly at that time of the year.

Boessenkool et al.51 used historic museum skins and contemporary blood samples to determine the effective population sizes of yellow-eyed penguins of the separate Management Units. They found very low effective population sizes (in the low hundreds), coupled with low immigration rates, supporting concern for the species, especially for the mainland population. Lopes & Boessenkool52 also applied a Bayesian coalescent approach using microsatellites and gene sequences derived from each management unit, suggesting that populations on sub-Antarctic islands have remained stable over the past 500 years. Genomic markers (such as whole genomes or Single Nucleotide Polymorphisms) from each management unit may also provide useful projections of past, present and future population sizes that cannot be detected from microsatellite loci alone and could contribute to understanding population trends.

The mainland population has been subject to several adult die-off events in the past three decades. The first major die-off event occurred in 1989 when penguin numbers on the Otago Peninsula declined by 62%53 followed by a further die-off in 200110. Another significant event occurred in February 2013, which resulted in a 41% drop in penguin numbers on the Otago Peninsula. To date, the cause of these die-offs remains unclear although the involvement of a toxic agent has been confirmed54. Harmful algal blooms have been suggested as a potential toxin origin (e.g. Trudi Webster7) yet plankton samples taken during the 2013 die-off found no trace of toxic algae in the marine environment (Philip Seddon, unpublished data).


Almost all yellow-eyed penguins breeding on Otago Peninsula have been banded and monitored for nearly 35 years, so there is a robust understanding of the species’ main demographic parameters10. Based on a Bayesian mark-recapture model, the median annual survival rate of adult yellow-eyed penguins on the New Zealand mainland is 87.4% (credible interval: 83.2%-90.4%). Since the mid-1990s, adult survival has been lower than the long-term average (determined from data dating back to the early 1980s). The low survival rates are to some extent associated with ocean warming10. Since the mid-1990s, the mean age of first-time breeders has declined suggesting that the pool of birds available for recruitment into the breeding population has diminished in the past 20 years10. It also appears as if the mainland population may have a gender imbalance, with male penguins outnumbering females (Melanie Young, pers. comm.)

Modelling showed the first-year survival rate of chicks to be very low, ranging between 7% and 19% (median: 12.4%)10. Another study put the first year survival rate slightly higher at 17.2%, and found that only 10.2% of fledged chicks became successful breeders55.

There is no equivalent demography data available for the sub-Antarctic yellow-eyed penguin populations.

Breeding biology

Breeding biology is by far the best-studied aspect of yellow-eyed penguin biology. Lance Richdale provided first comprehensive insights into the species’ breeding ecology1–3. Studies in the past 30 years have tackled various aspects of breeding behaviour, including nest site selection50,56,57, hormonal characteristics of breeding behaviour58,59, egg shell composition and incubation behaviour43,60,61, mate choice and parental investment29,62, and chick rearing strategies and feeding intervals63–66.

A very comprehensive summary of the breeding biology has been published by Seddon, Ellenberg & van Heezik12.

Yellow-eyed penguins breed in highly variable habitats that all share one characteristic: nests are visually isolated from other penguins56,57. The species prefers to breed in dense vegetation such as Hebe groves, patches of New Zealand flax (Phormium tenax & P. colensoi) or mature coastal forests. On Campbell Island the majority of nests were under a canopy of Dracophyllum, Myrsine or Coprosma43. An important determinant for the presence of yellow-eyed penguin colonies is suitable landing sites, which can be sandy or pebble beaches or rocky platforms50. Nests are usually established in shallow excavations lined with twigs, grass and leaves under scrub, at the base of flax plants or under tree roots and windfalls12.

Figure 2. Yellow-eyed penguin incubating freshly hatched chicks, Boulder Beach, Otago Peninsula (Photo: Thomas Mattern).

Figure 2. Yellow-eyed penguin incubating freshly hatched chicks, Boulder Beach, Otago Peninsula (Photo: Thomas Mattern).

Yellow-eyed penguins display high nest site fidelity in that adults tend to remain within a single breeding area50, usually establishing nets within 2-3 metres of previous nest sites; birds will defend territories of up to 10 m around their nest-sites (John Darby, pers. comm.). About three quarters of pairs remain together, but mate retention rates decline with the number of breeding seasons pairs stay together1. Death of one of the birds is the main cause of pair break-ups. Annual divorce rates not driven by mortality can range between 6-13%1,62.

Females enter the breeding population on average when 2.6 years old, while males start breeding at an average age of about 4.3 years1. Since the late 1990s, the age of first breeding has declined so that today a greater proportion of young birds make up the mainland breeding population10.

On the Otago Peninsula, the mean egg laying date is 24 September67. Further south egg laying can start later12. On Campbell Island yellow-eyed penguins commenced breeding on average 9 days later than the mainland population43.

The two eggs of most clutches are laid 3-5 days apart, although young females may only lay one egg1,50. Incubation starts after laying of the second egg; both parents share the incubation with incubation spells of around two days for both sexes64. Eggs are incubated for 39-51 days, which is the most variable incubation period among penguins1.

Hatching occurs synchronously in the first half of November1,68. 94% of two-egg clutches the eggs hatched within one day of each other50. The chick-rearing period has two phases: the chick-guard stage, during which the nest is constantly attended by one of the parents and lasts between 40 to 50 days, the post-guard stage during which chicks are left alone during the day while both parents forage to meet the increasing food demands of their offspring50,63,69. Chicks fledge about 106 days after hatching12.


Moult takes place from late February to late March although it has extended into April in recent years12. Shedding of old feathers and full growth of the new plumage takes about 24 days. Juveniles and non-breeding birds tend to moult earlier than breeding adults. Breeding penguins usually moult at or near their nest sites, while non-breeders and juveniles may moult as far north as Canterbury, Kaikoura and Cape Campbell.

Figure 3. Moulting hoiho.

Figure 3. Moulting Yellow-eyed penguin, Otago Peninsula, March 2006 (Photo: Thomas Mattern)

Food and foraging

The marine ecology of Yellow-eyed penguins was first investigated in the 1980s and early 1990s70–75, although these studies focussed principally on diet composition and foraging ranges. More sophisticated data logging technologies in the 2000s allowed reconstruction of at sea-movements in three-dimensions and highlighted the species affinity for benthic foraging8,31,32,76,77. At the time this report was written, further studies of the pre-moult and winter movements of adult and fledgling penguins were being conducted (Melanie Young, unpubl. data). As with other aspects of the species’ biology, most marine ecology studies have been conducted on the mainland, apart from a recent study of foraging behaviour at the Auckland Islands (Chris Muller, unpubl. data).

During the breeding season, mainland yellow-eyed penguins principally forage within 25 km from the coast31,32,71. While there is no marked difference in foraging ranges between incubation and chick rearing, the birds tend to stay at sea longer (14-65 hours, Moore, 1999) during incubation. During the chick rearing period, trip durations range from short evening trips (4 hours, Mattern et al., 2007) to full day-trips of 11 to 14 hours31,32,71. Outside the breeding period, penguins range further from their colony (Melanie Young, unpublished data) although their movements are still confined to the continental shelf where water depths do not exceed 160m. The deepest dive recorded so far is 161m, performed by a Yellow-eyed penguin from Campbell Island (Peter Moore, unpubl. data)

Of 46,948 dives recorded between 2003 and 2015 using GPS dive loggers on 71 yellow-eyed penguins from Oamaru, the Otago Peninsula, and Stewart and Codfish Islands during a total of 185 foraging trips, 54% were benthic dives (Mattern, unpubl. data). The majority of non-benthic dives occur during the home ward journey31. More recently the deployment of camera loggers on mainland yellow-eyed penguins revealed that pelagic foraging principally occurs if the environmental conditions are not conducive to bottom foraging78. During periods with increased algal blooms water clarity is reduced so that visibility at the seafloor is close to zero, forcing the penguins to search for prey in the upper regions of the water column. Under such circumstances, the penguins primarily ate larval and juvenile fish that seek protection from larger jellyfish. As soon as water clarity improved birds resumed benthic foraging78. The hypothesis that Yellow-eyed penguins may actually consume jellyfish79 seems unlikely in the light of recent findings.

When benthic foraging, Yellow-eyed penguins predominantly prey on demersal fish species. The first comprehensive study of the diet of mainland yellow-eyed penguin in the 1980s identified the main prey species to be red cod (Pseudophycis bacchus), opalfish (Hemerocoetes monopterygius) and, to a lesser extent, sprat (Sprattus antipodum), ahuru (Auchenoceros punctatus) and arrow squid (Nototodarus sloani)73,74. A change in the diet composition became apparent when red cod was replaced by blue cod and opalfish, with sprat and arrow squid again playing minor roles in terms of biomass brought ashore72. Recent deployments of camera loggers found that at the Otago Peninsula, opal fish and blue cod are now the single most dominant species; larval fish and sprat were only targeted during the period of environmentally forced pelagic foraging77,78,80.

There are regional differences in diet composition that may be related to the prevailing sediment structure of the seafloor within then Yellow-eyed penguins’ home ranges77. Penguins with access to coarse substrate such as gravel and coarse sand predominantly feed on opalfish, while in regions with well-defined benthic structures such as horse mussel fields, bryozoans, oyster beds or reefs the penguins principally ate blue cod (Parapercis colias) and red-banded perch (Hypoplectrodes huntii)77,81. The same seems to be true for regions that are exposed to seafloor fisheries. The disturbance caused by bottom trawls appears to attract scavenging species such as blue cod, which makes foraging in the wake of bottom trawls attractive to yellow-eyed penguins32. Regional differences in diet may occur on very small spatial scales. Camera logger deployments on penguins from two breeding areas along Stewart Island’s north-east coast (Rollers Beach -46.768°, 167.988°; Golden Beach -46.802°, 168.020°) found significant differences in prey composition even though these sites are only 5 km apart81. Penguins from Golden Beach fed predominantly on red-banded perch and juvenile tarakihi (Nemadactylus macropterus) while birds from Rollers Beach principally consumed blue cod.

While the calorific value of blue cod makes it a suitable prey item for adult yellow-eyed penguins, their large body size renders it a suboptimal food for chicks77. The commercial oyster fishery in Foveaux Strait may have contributed to a change in benthic biodiversity benefitting blue cod and causing penguin prey to switch with a concomitant decline in breeding success33.

Very little is known about diet composition and foraging ecology of yellow-eyed penguins on the sub-Antarctic islands. Underwater footage filmed at the Auckland Islands in 2016 shows five or six yellow-eyed penguins feeding on a dense school of bait fish77 suggesting that pelagic foraging could be more common there. GPS dive logger deployments of penguins on Enderby Island suggest that the birds forage within a 40-50 km radius east of the island; diving behaviour seems to consist of a mix of pelagic and benthic foraging (Chris Muller, unpubl. data). Dive recorder data from Campbell Island suggest a benthic foraging strategy (Peter Moore, unpubl. data).


Natural predators include sea lions (Phocarctos hookeri), sharks and, to a lesser, extent fur seals (Arctocephalus forsteri)85. Instances of sea lion predation have been recorded on Campbell Island42,48. Barracouta (Thyrsites atun) do occasionally inflict injuries to yellow-eyed penguins7. However, claims that barracouta are ‘main predators’87 likely exaggerate their impact. Camera logger observations of yellow-eyed penguins encountering schools of barracouta showed that the birds did not react to their presence81.


The breeding distribution of yellow-eyed penguins means that the majority of the mainland population occurs in areas close to urban centres or locations readily accessible to humans12. This exposes the penguins to a variety of anthropogenic threats.

Introduced predators

Terrestrial predators

NZ mainland: Major
Auckland Islands: Medium
Campbell Island: not a threat

On the mainland, Yellow-eyed penguins are exposed to an array of introduced terrestrial predators. Stoats (Mustela erminea) in particular prey on penguin eggs and chicks82. Ferrets (M. furo) and cats (Felis catus) are also thought to be yellow-eyed penguin predators12,50,83, although data on their true impact are lacking. Ratz & Murphy82 found that in comparison with stoats, the impact of cats and ferrets are minor. John Darby (pers. comm.) notes that trapping in the Boulder Beach complex in the 1980s resulted in 14 cats, 12 ferrets and two stoats being caught over a two-month period. Thereafter, stoats dominated the trap catch which could suggest that trapping may have changed the local predator guild benefitting stoats perhaps increasing predation on the penguins. A five-year study on Stewart Island investigating the impact of feral cats on the local yellow-eyed penguin populations found no conclusive evidence for any significant impact; instead starvation and disease were the dominant mortality factors84. Dogs (Canis familiaris) can kill adult penguins85 and unrestrained dogs pose a significant threat to yellow-eyed penguins85.

On the main Auckland Island, feral pigs (Sus scrofa) are believed to kill both adults and chicks5 perhaps explaining why few, if any yellow-eyed penguins still breed on the main island. A pig shot on Auckland Island contained the remains of a yellow-eyed penguin86. However, whether this was the result of active predation or scavenging of a dead penguin is unclear.

Since the successful eradication of Norway rats on Campbell Island, the region is now considered predator free87.

Fisheries interactions

Resource competition

NZ mainland: Major
Auckland Islands: Minor
Campbell Island: Minor

With the exception of blue cod and red cod, Yellow-eyed penguins principally prey on non-commercial fish species77. However, benthic habitats are subject to various bottom fisheries that in some areas have substantially altered the seafloor communities8. This has been found to reduce prey diversity and abundance89, alter feeding strategies32, and consequently affect penguin breeding success33 and population trajectories10. As such fisheries-related changes to the marine food web may contribute to a deterioration of the quality of the penguins’ diet77.

Incidental bycatch

NZ mainland: Major
Auckland Islands: Minor
Campbell Island: Minor

Yellow-eyed penguins are severely affected by set netting operations9. Their demersal foraging strategy makes them particularly prone to entanglement in set nets targeting rig and dogfish. In the 1990s, multiple captures of penguins in single nets were reported90. These catastrophic events may be indicative of the stochastic nature of set net bycatch. The likelihood of entanglement depends greatly on location and timing of the fishery, i.e. a net set within a penguin colony’s approach trajectory in the morning or afternoon will carry a much greater risk of multiple bycatch as penguins will be commuting to and from their foraging grounds.

There is a four-nautical mile set net ban around the South Island’s south-eastern coastline; however, Stewart Island and its outliers are exempt from this ban, so that nets may be set very close inshore and therefore across the main entry routes to penguin colonies. Conversely, a set net ban may result in set netting to occur further offshore where most yellow-eyed penguins forage.

The low-level of observer coverage for set net fishing vessels91,92 and likely under-reporting from other vessels, means that it is impossible to adequately assess the true level of bycatch mortality of Otago and Southland penguins. Considering the stochastic nature of the fishery’s impact, it seems unlikely that any meaningful information will come out of the observer program unless coverage is 100%. The presence of observers likely incentivises fishers to set nets in areas where bycatch risk (and potentially fishery yield) is low, while trips without observer on board may be used to fish where bycatch is more likely to occur but fishery yield may be higher as well.

Some yellow-eyed penguins have been caught in trawl nets7 although trawl bycatch appears to be less likely than set-net bycatch. Since set netting is not practised around either of the subantarctic islands, bycatch risk for Yellow-eyed penguins is probably low.

Die-off events / Unexplained mortality

NZ mainland: Major
Auckland Islands: unknown
Campbell Island: unknown

The periodic die-off events over the past three decades have decimated the breeding population on the Otago Peninsula10. Although dead yellow-eyed penguins with similar symptoms have been reported from other regions7, it appears that the main impact has been around the Otago Peninsula. Harmful algal blooms seem an unlikely explanation as such phenomena usually also impact other species93. Hence, climate-related or anthropogenic factors seem to be more likely to be the root cause of this problem. Possible causes could be accidental ingestion of toxic jellyfish (e.g. lion’s mane Cyanea capillata) during periods of algal bloom or the introduction of toxic agents from rivers or sewage outfalls10.

With only opportunistic monitoring being conducted on either of the subantarctic islands, it is unknown whether similar die-off events may have occurred.


Diphtheritic stomatitis

NZ mainland: Major
Auckland Islands: unknown
Campbell Island: unknown

Disease outbreaks in mainland yellow-eyed penguins have been reported since 2004 when chicks developed lesions in their oral cavity, which hampered food intake causing starvation, breathing difficulties, and occasional asphyxiation when lesions were inhaled. The disease has since been described as diphtheritic stomatitis and has occurred to varying extents since 200494. The disease seems to be associated with the presence of Corynabacterium amycolatum but a primary viral pathogen is suspected. The means of transmission have not been established94 although environmental stressors reducing the chicks’ immune response (e.g. starvation) could also be responsible12.

So far, there are no reports of the disease occuring on either Auckland or Campbell Islands. However, lack of frequent monitoring reduces the chance of detection of the disease.

Avian malaria

NZ mainland: Potentially major
Auckland Islands: unknown
Campbell Island: unknown

The protozoon Plasmodium is commonly associated with the occurrence of avian malaria95–97 but while high concentrations of antibodies to the parasite have been reported as early as 2007, malaria-related mortality events were not recorded98. The first cases of adult mortality due to avian malaria were reported from the Otago Peninsula during the 2017/18 breeding season, probably facilitated by an unusually high abundance of mosquitoes due to flood-related surface water and warm summer temperatures (Trudi Webster, pers. comm.).

Lack of monitoring prevents the risk assessment of avian malaria in the subantarctic region.


NZ mainland: not a threat
Auckland Islands: not a threat
Campbell Island: not a threat

Leucocytozoon have been reported from Yellow-eyed penguins throughout their entire range99,100 although it seldom is pathogenic96.

Climate change

While the effects have been found to play a major role in the decline of Yellow-eyed penguins on the mainland, the lack of research and monitoring efforts on the subantarctic islands makes it impossible to assess whether the southern populations are equally affected.

Ocean warming

NZ mainland: Major
Auckland Islands: unknown
Campbell Island: unknown

Recent population modelling has identified ocean warming to be a major driver of the current yellow-eyed penguin population decline10. In periods with higher than normal sea surface temperature (SST), adult survival rates are below average. Higher adult mortality resulting in new pairings with less experienced birds could explain why in seasons following warm years fewer fledglings are produced101. One third of variation in penguin numbers can be explained by ocean warming, which suggests other important, non-climatic factors are also involved.

Weather extremes (La Niña)

NZ mainland: Major
Auckland Islands: unknown
Campbell Island: unknown

The El Niño weather phenomenon usually coincides with lower than normal sea surface temperatures, which enhance yellow-eyed penguin survival rates due to favourable foraging conditions10. The opposite effect occurs during a La Niña events, which bring higher than normal SSTs and reduction in adult survival. Starvation events and avian malaria mortality have also been associated with La Niña conditions7,98.

Human impacts


NZ mainland: Major
Auckland Islands: Medium
Campbell Island: unknown

The impact of human disturbance, principally through unregulated tourism and other visitors in or close to penguin breeding areas, has been well documented19–22,102,103. Yellow-eyed penguins are timid and easily disturbed by people even when the people are 100 m away21. People on a beach can prevent yellow-eyed penguins transiting between the ocean and their nest site22,103. Camera phones and selfie-sticks have increased the likelihood that visitors will get too close to birds or their nests104.

Even though the subantarctic islands’ limited accessibility for tourist reduces the disturbance risk for the species, concerns about the efficacy of visitor management protocol to the Auckland Islands have been raised103.

Research and monitoring activities also contribute to elevated stress levels in penguins although their impact is generally mitigated if approved research protocols are followed20. A study investigating the impact of research activities on individual fitness and life-time reproductive success found no indication of long-term adverse effects by researchers105.


NZ mainland: Major
Auckland Islands: unknown
Campbell Island: unknown

Marine pollution and its effect on penguins are extremely difficult to quantify with few attempts made to monitor this. Marine systems are dynamic so that continuous monitoring would be required to detect rapid changes in pollution levels. It has been suggested that yellow-eyed penguin die-off events may be related to temporally and spatially limited pollution events10. However, the lack of data makes it impossible to verify such claims.

The conversion from sheep to dairy farming has greatly increased pollution in many New Zealand’s rivers106, which will undoubtedly have flow-on effects for the coastal marine ecosystems yellow-eyed penguins rely upon.

Due to the spatial isolation from the mainland, none of these factors are relevant for the subantarctic population of Yellow-eyed penguins. To which extent global pollution problems (e.g. microplastics107) may affect the species on the Auckland and Campbell Islands remains unknown.

Research Priorities

In the face of significant population declines, robust documentation of population trends and demographic variables are vital. Despite being the best studied of the New Zealand penguin species, there is still a substantial knowledge gap when it comes to the yellow-eyed penguins’ marine ecology, especially how their foraging and subsequently breeding success is affected by changes in their marine environment. With the mainland population levels at their lowest and climate warming predicted for the coming decades, disease outbreaks may become an ever increasing but potentially manageable problem. However, it is critical to examine whether the increased susceptibility to disease is a direct effect of a changing climate or indeed a secondary response to a detriorating marine habitat (i.e. reduced prey abundance and/or quality).

1. Population monitoring


Comprehensive surveys of sub-Antarctic populations

The assumption that the sub-Antarctic populations provide an insurance should the species disappear from the mainland is largely based on 30-year-old information It is of utmost importance to investigate population size and trends on both sub-Antarctic island groups.

Investigate reliable automatic monitoring methods and repeat Peter Moore’s mark-recapture methods employed on Campbell & Auckland Islands in the 1980s and 1990s48.


Continue monitoring on the mainland

Maintaining the monitoring effort at sites with a long monitoring history (e.g. Boulder Beach) is essential. It is vital to identify as many of the breeding individuals each year to derive demographic parameters such as survival and recruitment rates10.


Investigate the viability of automated ID gateways

Automatic monitoring solutions have proven to be reliable in determining demographic parameters and population trends in other penguin species108,109. Transponder gates not only allow effective identification of breeding populations but also provide additional information about nest attendance patterns and foraging trip lengths. These are particularly in regions such as the Catlins and Stewart Island where there is limited monitoring effort. Automatic solutions could provide critical information about population parameters that are currently principally extrapolated from monitored sites in Otago10.

Trial the viability and reliability of transponder gates at suitable site, e.g. Penguin Bay and Hinahina Cove, Catlins.


Investigate the effects of diseases on key demographic parameters, especially adult survival and recruitment

While disease management is an important conservation tool that will likely increase in importance with a warming climate7,95,96, the true impacts disease may have on yellow-eyed penguin populations remains unclear. Diphtheritic stomatitis is receiving management attention although it principally affects young chicks94 while adult survival and recruitment are the two key demographic parameters that determine population trends10. Consequently, the few adult deaths from avian malaria are probably of greater concern for the conservation of yellow-eyed penguins.


Investigate true impacts of predators

While the impact of cats, ferrets and barracouta are often cited as significant, factual evidence for these claims is missing or seems to indicate the opposite is true47. It is therefore vital to investigate the importance of the various species believed to prey on yellow-eyed penguins to ensure that conservation efforts target critical issues rather than over-emphasized claims. The influence the recovering sea lion populations have on survival rates of yellow-eyed penguins on the mainland requires consideration.


Examine viable methods to identify and subsequently control the cause of disease outbreaks, e.g. diet quality, climate change, disease vectors

The prevention of disease outbreaks is critical110. The causes of the frequent outbreaks of diphtheritic stomatitis are still unknown although it has been argued that it may be related to diet quality33,77. Regarding climate change, the abundance of disease vectors such as mosquitoes may become a serious problem for native wildlife in the future so that the development of methods for their control may become an essential management tool.

2. Marine Ecology


Monitoring of marine ecology: foraging behaviour & diet composition

Yellow-eyed penguins are primarily a marine species. Factors influencing their survival are likely marine based. The decades focused on terrestrial conservation efforts such as habitat regeneration and predator control have not resulted in recovery of the species on the New Zealand mainland10. Currently there is an increasing focus on the development of reactive management of disease events. Yet compared to other penguin species that are of equal economic importance (i.e. Little penguins, African penguins111–115), there is no concerted effort to investigate how marine-based factors may not only influence survival rates and population trends of yellow-eyed penguins, but also may provide new insights into mechanisms that potentially contribute or even be root causes of disease outbreaks (e.g. diet composition, food quality, pathogens).

Initiate a marine ecology monitoring programme that provides baseline information on foraging behaviour and foraging success (i.e. using GPS dive loggers) as well as diet composition (i.e. via faecal DNA analysis & animal-borne cameras) to supplement population monitoring and allow investigation of the importance of sea-based factors in causing poor breeding success, mortality events and disease outbreaks.


Quantify fisheries impacts on mainland population

The difficulties of assessing fisheries impacts on yellow-eyed penguins has already been highlighted10. Quantifiable data on fisheries interactions is vital but can only be achieved through the implementation of better control mechanisms of the inshore fishing fleet. Video observation of set netting vessels may help to quantify the true impact of bycatch mortality on penguin populations.


Investigate state of the benthic habitat

Investigate state of the benthic habitat within the species’ core foraging regions, perhaps by mapping seafloor biodiversity and quantify habitat degradation caused by fishing activity using animal-borne cameras and multi-beam surveys.


Foraging behaviour of fledgling penguins

Yellow-eyed penguins have one of the lowest first-year survival rates of all penguin species. It is therefore important to gain a better understanding of the at-sea behaviour, distributions and foraging success of penguins during their first year. Hence, the investigation of methods to study diving behaviour and diet composition during the crucial first year at sea is of considerable importance.


Foraging ecology of sub-Antarctic penguins

Conduct a baseline study of the foraging ecology – foraging ranges, diving behaviour and diet composition – of breeding yellow-eyed penguins from the sub-Antarctic Islands, particularly Campbell Island where bathymetry does not seem conducive to a benthic foraging strategy. Investigate whether the species occupies different oceanic niches to mainland penguins, which may be key for the survival of the species in the face of climate change.


Conduct comprehensive studies on the critical pre-moult and winter movements of Yellow-eyed penguins throughout their entire range

The pre-moult period is the most critical stage of any penguin species’ annual lifecycle. During a relatively brief time period between the end of breeding and the onset of the moult, it is vital for penguins to replenish body resources quickly to increase the chance of survival during the energy demanding moulting period. Knowing where Yellow-eyed penguins find their food as well as the composition of their diet is vital for any efforts to protect the species in its marine habitat.

Study foraging ranges and diving behaviour using GPS dive loggers; investigate diet composition via faecal sampling, stable isotope analysis.

3. Disease Monitoring


Investigate potential ecological factors facilitating the occurrence of diphtheritic stomatitis in chicks, e.g. diet composition during egg formation and early chick rearing phase.


Monitor the prevalence of avian malaria in the mainland population of Yellow-eyed penguins and investigate potential disease vectors and mitigation methods.


Monitor for outbreaks of diphtheritic stomatitis and develop best-practice protocols for the treatment of infected chicks (e.g. debriding of lesions).


We thank Peter Moore, John Darby, Yolanda van Heezik, Trudi Webster, Tess Cole, Bruce McKinlay, Dave Houston, and Phil Seddon for critical comments on early drafts of this account. This review was funded by the T-Gear Charitable Trust and the Birds-New Zealand Research Fund. Thanks so much for supporting our work. We are especially grateful to Peter Gaze for his support and interest throughout.


  1. Richdale, LE. (1957) A population study of penguins. (Clarendon Press).
  2. Richdale, LE. (1951) Sexual behavior in penguins. (University of Kansas Press).
  3. Richdale, LE. (1949) A study of a group of penguins of known age. (Otago Daily Times and Witness Newspapers Company).
  4. Marchant, S & Higgins, PJ. (1990) Megadyptes antipodes Yellow-eyed penguin. in Handbook of Australian, New Zealand and Antarctic Birds, Vol 1A: Ratites to Ducks 236–246 (Oxford University Press).
  5. Taylor, GA. (2000) Action Plan for Seabird Conservation in New Zealand. Part A: Threatened Seabirds. Department of Conservation, New Zealand. Wellington.
  6. McKinlay, B. (2001) Hoiho (Megadyptes antipodes) reovery plan, 2000-2025. Threatened Species Recovery Plan No. 35 Department of Conservation. Wellington, New Zealand.
  7. Webster, T. (2018) The Pathway ahead for hoiho. Dunedin, New Zealand.
  8. Ellenberg, U & Mattern, T. (2012) Yellow-eyed penguin - review of population information. Report POP2011-08. Conservation Services Programme, Department of Conservation. Wellington, New Zealand. DOI:
  9. Crawford, R et al. (2017) Tangled and drowned: A global review of penguin bycatch in fisheries. Endangered Species Research 34: 2017 DOI:
  10. Mattern, T et al. (2017) Quantifying climate change impacts emphasises the importance of managing regional threats in the endangered Yellow-eyed penguin. PeerJ 5: e3272 DOI:
  11. Massaro, M & Blair, D. (2003) Comparison of population numbers of yellow-eyed penguins, Megadyptes antipodes, on Stewart Island and on adjacent cat-free islands. New Zealand Journal of Ecology 27: 107–113
  12. Seddon, PJ, Ellenberg, U & van Heezik, Y. (2013) Yellow-eyed penguin (Megadyptes antipodes). in Penguins: Natural History and Conservation (eds. Garcia Borboroglu, P. & Boersma, P. D.) 91–110 (University of Washington Press).
  13. Boessenkool, S et al. (2009) Relict or colonizer? Extinction and range expansion of penguins in southern New Zealand. Proceedings of the Royal Society B: Biological Sciences 276: 815–821 DOI:
  14. Boessenkool, S, Star, B, Waters, JM & Seddon, PJ. (2009) Multilocus assignment analyses reveal multiple units and rare migration events in the recently expanded yellow‐eyed penguin (Megadyptes antipodes). Molecular ecology 18: 2390–2400
  15. Rawlence, NJ et al. (2015) Radiocarbon-dating and ancient DNA reveal rapid replacement of extinct prehistoric penguins. Quaternary Science Reviews 112: 59–65 DOI:
  16. Triggs, S & Darby, JT. (1989) Genetics and Conservation of the Yellow-Eyed Penguin. Science and Research Internal Report No. 43. Wellington, New Zealand.
  17. Darby, JT. (2003) The yellow-eyed penguin (Megadyptes antipodes) on Stewart and Codfish Islands. Notornis 50: 148–154
  18. Moore, PJ. (2001) Historical records of yellow-eyed penguin (Megadyptes antipodes) in southern New Zealand. Notornis 48: 145–156
  19. Ellenberg, U, Setiawan, AN, Cree, A, Houston, DM & Seddon, PJ. (2007) Elevated hormonal stress response and reduced reproductive output in Yellow-eyed penguins exposed to unregulated tourism. General and comparative endocrinology 152: 54–63 DOI:
  20. Ellenberg, U, Mattern, T & Seddon, P. (2009) Habituation potential of yellow-eyed penguins depends on sex, character and previous experience with humans. Animal Behaviour 77: 289–296 DOI:
  21. Ellenberg, U, Mattern, T & Seddon, PJPJ. (2013) Heart rate responses provide an objective evaluation of human disturbance stimuli in breeding birds. Conservation Physiology 1: cot013 DOI:
  22. McClung, MR, Seddon, PJ, Massaro, M & Setiawan, AN. (2004) Nature-based tourism impacts on yellow-eyed penguins Megadyptes antipodes: does unregulated visitor access affect fledging weight and juvenile survival? Biological Conservation 119: 279–285
  23. Robertson, HA et al. (2017) Conservation status of New Zealand birds, 2016. New Zealand Threat Classification Series 19: 26 p. Available at:
  24. BirdLife International. (2016) Megadyptes antipodes. The IUCN Red List of Threatened Species e.T22697800A93640603 DOI:
  25. Moore, PJ et al. (1995) Yellow-eyed penguin foraging study, south-eastern New Zealand, 1991-1993. Department of Conservation. Available at Wellington, N.Z. Available at:
  26. Efford, MG, Spencer, N & Darby, JT. (1994) A relational database for Yellow-eyed penguin banding and breeding records. Landcare Research, Dunedin, New Zealand. unpublished report.
  27. Efford, MG, Spencer, NJ & Darby, JT. (1996) Population studies of Yellow-eyed penguins - 1994-94 progress report. Department of Conservation. Wellington.
  28. McKinlay, B. (1997) The conservation of Yellow-eyed penguins (Megadyptes antipodes): use of a PVA model to guide policy development for future conservation management direction. (Department of Zoology, University of Otago).
  29. Edge, KA, Jamieson, IG & Darby, JT. (1999) Parental investment and the management of an endangered penguin. Biological Conservation 88: 367–378
  30. Mattern, T, Ellenberg, U & Davis, LS. (2007) Decline for a Delicacy: Are decreasing numbers of Yellow-eyed penguins on Stewart Island a result of commercial oyster dredging. in 6th International Penguin Conference DOI:
  31. Mattern, T, Ellenberg, U, Houston, DM & Davis, LS. (2007) Consistent foraging routes and benthic foraging behaviour in yellow-eyed penguins. Marine Ecology Progress Series 343: 295–306 DOI:
  32. Mattern, T et al. (2013) Straight line foraging in yellow-eyed penguins: new insights into cascading fisheries effects and orientation capabilities of marine predators. PLOS ONE 8: e84381 DOI:
  33. Browne, T, Lalas, C, Mattern, T & Van Heezik, Y. (2011) Chick starvation in yellow-eyed penguins: Evidence for poor diet quality and selective provisioning of chicks from conventional diet analysis and stable isotopes. Austral Ecology 36: 99–108 DOI:
  34. Couch-Lewis, Y, McKinlay, B, Murray, SJ & Edge Hill, K-A. (2016) Yellow-eyed Penguin Stock-Take Report - He purongo mo te Hoiho - A report of progress against the Hoiho Recovery Plan (Department of Conservation, 2000) objectives and actions. Dunedin, New Zealand.
  35. Worthy, TH. (1997) The identification of fossil Eudyptes and Megadyptes bones at Marfells Beach, Marlborough, South Island. New Zealand Natural Sciences 23: 71–85
  36. Worthy, TH. (1998) A remarkable fossil and archaeological fauna from Marfell’s Beach, Lake Grassmere, South Island, New Zealand. Records of the Canterbury Museum 12: 79–176
  37. Worthy, TH. (1999) What was on the menu - avian extinction in New Zealand. New Zealand Journal of Archaeology 19: 125–160
  38. Worthy, TH & Holdaway, RN. (2002) The Lost World of the Moa, Prehistoric Life of New Zealand. (Canterbury University Press).
  39. Cole, TL et al. (2019) Ancient DNA of crested penguins: Testing for temporal genetic shifts in the world’s most diverse penguin clade. Molecular Phylogenetics and Evolution 131: 72–79 DOI:
  40. Moore, PJ. (1992) Population estimates of Yellow-eyed Penguin (Megadyptes antipodes) on Campbell and Auckland Islands 1987-90. Notornis 39: 1–15
  41. Beer, K. (2010) Distribution of Yellow-eyed Penguins (Megadyptes antipodes) on the Auckland Islands. Dunedin, New Zealand.
  42. Moore, PJ & Moffat, RD. (1990) Yellow-eyed penguin on Campbell Island. Wellington, New Zealand.
  43. Moore, PJ. (1992) Breeding biology of the yellow-eyed penguin Megadyptes antipodes on Campbell Island. Emu 92: 152–167 DOI:
  44. Department of Conservation. (2015) Yellow-eyed penguin database.
  45. Marchant, S & Higgins, PJ. (1990) Megadyptes antipodes Yellow-eyed penguin. in Handbook of Australian, New Zealand and Antarctic Birds, Vol 1A: Ratites to Ducks 236–246 (Oxford University Press).
  46. Houseman, M. (2018) Spatial Structure and Population Dynamics of Yellow-eyed Penguins (Megadyptes antipodes) on New Zealand Mainland. (University of Otago).
  47. King, SD. (2008) Breeding success of Yellow-eyed penguins on Stewart Island and off-shore islands 2003-2008. Dunedin, New Zealand.
  48. Moore, PJ, Fletcher, D & Amey, J. (2001) Population estimates of Yellow-eyed Penguins, Megadyptes antipodes, on Campbell Island, 1987-98. Emu 101: 225–235 DOI:
  49. Chilvers, B. (2014) Changes in annual counts of yellow-eyed penguins (Megadyptes antipodes) at Sandy Bay, Enderby Island, 2001 - 2012. Notornis 61: 103–105
  50. Darby, JT & Seddon, PJ. (1990) Breedig biology of Yellow-eyed Penguins (Megadyptes antipodes). in Penguin Biology (eds. Davis, L. S. & Darby, J. T.) 45–62 (Academic Press).
  51. Boessenkool, S, Star, B, Seddon, PJ & Waters, JM. (2010) Temporal genetic samples indicate small effective population size of the endangered yellow-eyed penguin. Conservation Genetics DOI:
  52. Lopes, JS & Boessenkool, S. (2010) The use of approximate Bayesian computation in conservation genetics and its application in a case study on yellow-eyed penguins. Conservation Genetics DOI:
  53. Gill, JM & Darby, JT. (1993) Deaths in yellow-eyed penguins (Megadyptes antipodes) on the Otago Peninsula during the summer of 1990. New Zealand Veterinary Journal 41: 39–42
  54. Gartrell, B et al. (2016) Investigation of a mortality cluster in wild adult yellow-eyed penguins (Megadyptes antipodes) at Otago Peninsula, New Zealand. Avian Pathology 0: 1–26 DOI:
  55. Stein, AM, Young, MJ, Darby, JT, Seddon, PJ & van Heezik, Y. (2017) Evidence for high inter-generational individual quality in yellow-eyed penguins. PeerJ 5: e2935 DOI:
  56. Seddon, PJ & Davis, LS. (1989) Nest site selection by Yellow-yed penguins. Condor 91: 653–659
  57. Clark, RD, Mathieu, R & Seddon, PJ. (2015) Selection for protection from insolation results in the visual isolation of Yellow-eyed Penguin Megadyptes antipodes nests. Bird Conservation International 25: 192–206 DOI:
  58. Cockrem, JF & Seddon, PJ. (1994) Annual Cycle of Sex Steroids in the Yellow-Eyed Penguin (Megadyptes antipodes) on South Island, New Zealand. General and Comparative Endocrinology 94: 113–121 DOI:
  59. Setiawan, AN et al. (2006) Hormonal correlates of parental behavior in yellow-eyed penguins (Megadyptes antipodes). Comparative Biochemistry and Physiology - A Molecular and Integrative Physiology 145: 357–362 DOI:
  60. Massaro, M, Darby, JT, Davis, LS, Edge, KA & Hazel, MJ. (2002) Investigation of interacting effects of female age, laying dates, and egg size in yellow-eyed penguins (Megadyptes antipodes). The Auk 119: 1141 DOI:
  61. Massaro, M & Davis, LS. (2004) Preferential incubation positions for different sized eggs and their influence on incubation period and hatching asynchrony in Snares crested (Eudyptes robustus) and yellow-eyed penguins (Megadyptes antipodes). Behavioral Ecology and Sociobiology 56: 426–434 DOI:
  62. Setiawan, AN, Massaro, M, Darby, JT & Davis, LS. (2005) Mate and territory retention in yellow-eyed penguins. Condor 107: 703–709 DOI:[0703:MATRIY]2.0.CO;2
  63. Schuster, K & Darby, JT. (2000) Observations on the chick-rearing strategy of yellow-eyed penguins (Megadyptes antipodes) on Otago Peninsula, New Zealand. Notornis 47:
  64. Seddon, PJ. (1989) Patterns of nest relief during incubation, and incubation variability in the Yellow-eyed penguin (Megadyptes antipodes). 16: 393–400
  65. Seddon, PJ. (1990) Behaviour of the yellow-eyed penguin chick. Journal of Zoology 220: 333–343 DOI:
  66. Seddon, PJ. (1991) An ethogram for the Yellow-eyed Penguin. Marine Ornithology 19: 109–115
  67. van Heezik, Y. (1988) Growth and diet of the Yellow-eyed penguin, Megadyptes antipodes. PhD:
  68. Darby, JT. (1989) Seabird monitoring in New Zealand. in Proceedings of a symposium on environmental monitoritzg in New Zealand (ed. Craig, B.) 235–239 (Department of Conservation, New Zealand).
  69. Seddon, PJ & Darby, JT. (1990) Activity budget for breeding yellow-eyed penguins. New Zealand Journal of Zoology 17: 527–532
  70. Seddon, PJ & van Heezik, Y. (1990) Diving Depths of the Yellow-eyed penguin Megadyptes antipodes. Emu 90: 53–57
  71. Moore, PJ. (1999) Foraging range of the Yellow-eyed penguin Megadyptes antipodes. Marine Ornithology 27: 49–58
  72. Moore, PJ & Wakelin, MD. (1997) Diet of the Yellow-eyed penguin Megadyptes antipodes, South Island, New Zealand, 1991-1993. Marine Ornithology 25: 17–29
  73. van Heezik, Y. (1990) Seasonal, geographical, and age-related variations in the diet of the Yellow-eyed Penguin (Megadyptes antipodes). New Zealand Journal of Zoology 17: 201–212
  74. van Heezik, Y & Davis, LS. (1990) Effects of food variability on growth rates, fledging sizes and reproductive success in the Yellow‐eyed Penguin Megadyptes antipodes. Ibis 132: 354–365
  75. van Heezik, Y. (1990) Diets of yellow-eyed, Fiordland crested, and little blue penguins breeding sympatrically on Codfish Island, New Zealand. New Zealand Journal of Zoology 17: 543–548
  76. Chilvers, B, Dobbins, M & Edmonds, H. (2014) Diving behaviour of yellow-eyed penguins, Port Pegasus/Pikihatiti, Stewart Island/Rakiura, New Zealand. New Zealand Journal of Zoology 41: 161–170 DOI:
  77. Mattern, T & Ellenberg, U. (2018) Yellow-eyed penguin diet and indirect effects on prey composition – Collation of biological information (CSP16205-1, POP2016-05). (Department of Conservation, New Zealand). DOI:
  78. Mattern, T, Ellenberg, U, Van Heezik, Y & Seddon, PJ. (2017) Penguins hunting jellyfish: main course, side dish or decoration? 3rd World Seabird Twitter Conference DOI:
  79. Thiebot, J-B et al. (2017) Jellyfish and other gelata as food for four penguin species - insights from predator-borne videos. Frontiers in Ecology and the Environment 15: 437–441 DOI:
  80. Mattern, T, McPherson, MD, Ellenberg, U, van Heezik, Y & Seddon, PJ. (2018) High definition video loggers provide new insights into behaviour, physiology, and the oceanic habitat of a marine predator, the yellow-eyed penguin. PeerJ 6: e5459 DOI:
  81. Seed, R, Mattern, T, Ellenberg, U, McPherson, M & Seddon, PJ. (2018) Identifying key benthic habitats and associated behaviours in foraging Yellow-eyed penguins (Megadyptes antipodes). Dunedin, New Zealand.
  82. Ratz, H & Murphy, B. (1999) Effects of habitat and introduced mammalian predators on the breeding success of Yellow-eyed Penguins Megadyptes antipodes, South Island, New Zealand. Pacific Conservation Biology 5: 16–27 DOI:
  83. Clapperton, BK. (2001) Advances in New Zealand mammalogy 1990–2000: Feral ferret. Journal of the Royal Society of New Zealand 31: 185–203 DOI:
  84. King, SD et al. (2012) Site-specific reproductive failure and decline of a population of the Endangered yellow-eyed penguin: a case for foraging habitat quality. Marine Ecology Progress Series 467: 233
  85. Hocken, AG. (2005) Necropsy findings in yellow-eyed penguins (Megadyptes antipodes) from Otago, New Zealand. New Zealand Journal of Zoology 32: 1–8 DOI:
  86. Challies, CN. (1975) Feral pigs (Sus scrofa) on auckland island: Status, and effects on vegetation and nesting sea birds. New Zealand Journal of Zoology DOI:
  87. McClelland, P. (2011) Campbell Island – pushing the boundaries of rat eradications. in Island invasives: eradication and management (eds. Veitch, C., Clout, M. & Towns, D.) 204–207 (IUCN).
  88. White, S. (2017) Marine reserve ‘big step backwards’. Otago Daily Times Available at:‘big-step-backwards’.
  89. Cranfield, HJ, Michael, KP & Doonan, IJ. (1999) Changes in the distribution of epifaunal reefs and oysters during 130 years of dredging for oysters in Foveaux Strait, southern New Zealand. Aquatic Conservation: Marine and Freshwater Ecosystems 9: 461–483 DOI:
  90. Darby, JT & Dawson, SM. (2000) Bycatch of yellow-eyed penguins (Megadyptes antipodes) in gillnets in New Zealand waters 1979–1997. Biological Conservation 93: 327–332
  91. Ramm, K. (2012) Conservation services programme observer report, 1 July 2009 to 30 June 2010. Wellington, New Zealand.
  92. Richard, Y & Abraham, ER. (2015) Assessment of the risk of commercial fisheries to New Zealand seabirds, 2006–07 to 2012–13. Wellington, New Zealand. Available at:
  93. Shumway, SE, Allen, SM & Boersma, PD. (2003) Marine birds and harmful algal blooms: Sporadic victims or under-reported events? Harmful Algae 2: 1–17 DOI:
  94. Alley, MR et al. (2017) Diphtheritic stomatitis in yellow-eyed penguins (Megadyptes antipodes) in New Zealand. Journal of Wildlife Diseases 53: 102–110 DOI:
  95. Grilo, ML et al. (2016) Malaria in penguins – current perceptions. Avian Pathology 45: 393–407 DOI:
  96. Vanstreels, RET, Braga, ÉM & Catão-Dias, JL. (2016) Blood parasites of penguins: A critical review. Parasitology 143: 931–956 DOI:
  97. Graczyk, TK, Cockrem, JF, Cranfield, MR, Darby, JT & Moore, P. (1995) Avian malaria seroprevalence in wild New Zealand penguins. Parasite 2: 401–405
  98. Sturrock, HJW & Tompkins, DM. (2007) Avian malaria (Plasmodium spp) in yellow-eyed penguins: Investigating the cause of high seroprevalence but low observed infection. New Zealand Veterinary Journal 55: 158–160 DOI:
  99. Hill, A, Howe, L, Gartrell, B & Alley, M. (2010) Prevalence of Leucocytozoon spp, in the endangered yellow-eyed penguin Megadyptes antipodes. Parasitology 137: 1477–1485 DOI:
  100. Argilla, LS, Howe, L, Gartrell, BD & Alley, MR. (2013) High prevalence of Leucocytozoon spp. in the endangered yellow-eyed penguin (Megadyptes antipodes) in the sub-Antarctic regions of New Zealand. Parasitology 140: 672–682 DOI:
  101. Peacock, L, Paulin, M & Darby, JT. (2000) Investigations into the climate influence on population dynamics of yellow-eyed penguins Megadyptes antipodes. New Zealand Journal of Zoology 27: 317–325
  102. Ellenberg, U, Mattern, T, Seddon, PJ & Jorquera, GL. (2006) Physiological and reproductive consequences of human disturbance in Humboldt penguins: The need for species-specific visitor management. Biological Conservation 133: 95–106 DOI:
  103. French, R, Muller, C, Chilvers, B & Battley, P. (2018) Behavioural consequences of human disturbance on subantarctic Yellow-eyed Penguins Megadyptes antipodes. Bird Conservation International 1–14 DOI:
  104. Shawn McAvinue. (2017) Penguin selfies ‘not cool’. Otago Daily Times Available at:
  105. Stein, A, Young, MJ, Seddon, PJ, Darby, JT & van Heezik, Y. (2017) Investigator disturbance does not reduce annual breeding success or lifetime reproductive success in a vulnerable long-lived species, the yellow-eyed penguin. Biological Conservation DOI:
  106. Davies-Colley, RJ. (2013) River water quality in New Zealand: An introduction and overview. in Ecosystem Services in New Zealand – Conditions and Trends 432–447
  107. Ropert-Coudert, Y et al. (2019) Happy Feet in a Hostile World? The Future of Penguins Depends on Proactive Management of Current and Expected Threats. Frontiers in Marine Science 6: DOI:
  108. Gendner, J-P, Gauthier-Clerc, M, Bohec, C Le, Descamps, S & Maho, Y Le. (2005) A New Application for Transponders in Studying Penguins / Un nuevo uso de equipo electrónico (transponders) para estudiar pingüinos. Journal of Field Ornithology DOI:
  109. Descamps, S, Bohec, C Le, Maho, Y Le, Gendner, J-P & Gauthier-Clerc, M. (2009) Relating Demographic Performance to Breeding-Site Location in the King Penguin. The Condor DOI:
  110. Wobeser, G. (2002) Disease management strategies for wildlife. Revue Scientifique et Technique-Office international des epizooties 21: 159–178 DOI:
  111. Pelletier, L, Chiaradia, A, Kato, A & Ropert-Coudert, Y. (2014) Fine-scale spatial age segregation in the limited foraging area of an inshore seabird species, the little penguin. Oecologia 176: 399–408 DOI:
  112. Saraux, C, Chiaradia, A, Salton, M, Dann, P & Viblanc, VA. (2016) Negative effects of wind speed on individual foraging performance and breeding success in little penguins. Ecological Monographs 86: 61–77 DOI:
  113. Sherley, RRB et al. (2013) Influence of local and regional prey availability on breeding performance of african penguins spheniscus demersus. Marine Ecology Progress Series DOI:
  114. Sherley, RB et al. (2017) Metapopulation Tracking Juvenile Penguins Reveals an Ecosystem-wide Ecological Trap. Current Biology DOI:
  115. Sherley, RB et al. (2018) Bayesian inference reveals positive but subtle effects of experimental fishery closures on marine predator demographics. Proceedings of the Royal Society B: Biological Sciences DOI: